Manway cover with integrally formed vent

ABSTRACT

A venting solution to large storage tanks is disclosed wherein a manway cover is formed with a vent, eliminating the need to affix a vent to the wall of the tank and allowing standardized manway covers with different vent sizes to be applied either in a retrofit or in new tanks. The covers can be formed two at a time to increase production, and can be fitted with a larger vent than would otherwise be practical with some tank diameters.

BACKGROUND

In many industries such as chemical, waste water, food processing, and the like, large tanks are used to store liquid materials until they are needed or until they can be disposed. These storage tanks may be made of fiberglass, polyethylene, polypropylene, PVC, stainless steel, bolted steel, or a dual laminate, depending upon the application and requirements of the various industries. The tanks are typically stored in groups, as shown generally in FIG. 1, and can range in size from one hundred gallons to four hundred and fifty thousand gallons. Such tanks can be obtain from distributors such as Core-Rosion Products of Signal Hill, Calif.

While it was customary in the past to fill these tanks using gravity (i.e., simply pouring material into the tanks), newer technology has allowed these tanks to be filled by pressurized tankers using pneumatic or hydraulic pressure to move the fluid. While increasing the efficiency in which the tanks are filled, these pressure driven systems require that the tanks be adequately “vented” to prevent damage due to over-pressurization of the tanks. Over-pressurization can quickly lead to cracks or even rupture of the tanks, which can be problematic in the best case and disastrous when toxic or caustic chemicals are involved. For this reason, it has been customary to incorporate designated vents into the tanks that permit air to escape as liquid is forced into the tanks at high speed. A classic vent type is the “u”-shaped vents that can be mounted on to the tops of the tanks, such as those shown in FIG. 1.

While these vents have become commonplace on the storage tanks described above, the difficulty with the prior art vents is that there is often a challenge to mount the vents to the tanks in a safe and efficient manner. Mismatch between materials, particularly with difficult materials such as fiberglass or polypropylene, make mounting and securing a vent to the tank both costly and unreliable. This problem is exacerbated by tanks that have different contours and shapes, preventing a “one-size-fits-all” solution. For these reasons, the vents for these tanks tend to be expensive and difficult to install.

SUMMARY OF THE INVENTION

The problems of tank venting discussed above are overcome by the present invention, in which a manway cover having standard sizes and dimensions for tanks of this kind is formed with a vent therein, ensuring that the vent will mate with and easily attach to the tank in a reliable manner. Further, enhanced cost savings are realized when the vent is integrally formed with the manway cover in a single molding process. A single piece mold of a multi-diameter manway cover and vent can reliable fit existing and new tanks and eliminate the need for tank specific venting solutions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated, perspective view of tanks of the prior art;

FIG. 2 is an elevated, perspective view of a first embodiment of the present invention;

FIG. 3 is a cross-sectional, enlarged view of the manway cover and vent mounted on a tank;

FIG. 4 is another cross-sectional view of a manway cover and vent mounted on a tank; and

FIG. 5 is a side view of a molded dual cover design showing a smaller and larger cover made from a single mold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates the environment of the present invention, showing prior art solutions to the venting problem encountering the filling of large reservoirs or “tanks” 10 used to store fluids in various industries. These storage tanks 10 are typically cylindrical, with a conical upper portion 12 that includes a manway cover 14 at the center. Manway covers 14 allow workers or maintenance personnel to climb into the tanks to clean, repair, or otherwise access the inner volume of the tanks, and manways have standard sizes in the industry such as fourteen inches (14″), eighteen inches (18″), and twenty-two inches (“22″). The manway covers 14 seal the tank and also can be used as a port to fill the tank 10. As the tanks 10 are filled, vents 16 are incorporated into the tanks 10 to allow the tanks to depressurize as it is being filled with fluid. As fluid or material fills the tank, air is forced out of the tank through the vent 16 so that the tank does not experience over-pressurization during the filling operation. Unfortunately, as set forth above, the vents 16 must be mounted on the tanks by cutting the tank 10 and bolting or otherwise affixing the vent 16 to the upper portion 12 of the tank near its highest point so that fluid cannot escape through the vent 10. This mounting operation has led to problems with cost and reliability in mating the two structures.

FIG. 2 shows a tank 10 with a manway cover 30 and a mushroom vent 32 formed as a single unit. The manway cover 30 with built-in vent 32 avoids having to implement a vent into the tank itself. The manway cover 30 can vent through the mushroom vent 32 while material or fluid is filled through a filling port (not shown), leading to less problems with the tank/vent interface. FIGS. 3 and 4 show a cross-sectional view of the manway cover 30 and mushroom vent 32 of FIG. 2. The cover 30 bolts to the tank 10 using fasteners 34 to seal the cover to the tank 10. The cover 30 includes a central stem 36 onto which the vent 32 is mounted, either through a mechanical fit such as threads, detents, interference fit, etc., fasteners, or an adhesive fit. The vent 32 can preferably be fitted with screens 38 to prevent birds or other animals from entering into the tank 10 through the vent. With the vent disposed over the stem 36, the tank can vent properly with the atmosphere while the tank is being filled through the manway cover 30.

The manway cover 30 and vent 32 can be retrofitted to existing tanks as well as incorporated into new tanks. The stem 36 is preferably made with a standard OD, enabling the vent to be used with standard tank adapters. The stem 36 may also include a standalone flange 42 mounting plate to allow its use with other existing tank arrangements. The flange 42 can be removed when used in the configuration of FIG. 3, but used in other configurations to bolt the standalone vent 32 to the tank 10. Another advantage of the current design is that it allows large vents to be installed on all size diameter tanks using the manway cover as the location of the vent.

FIG. 5 shows a set of two manway covers being formed back-to-back using a molding process, where each cover is of different sizes. Of course, both covers could also be the same size using this process. This molding design allows twice as many covers 30 a,b to be formed with each molding process. The molded design of FIG. 5 has a first circumferential cover 30 a mated to a second circumferential cover 30 b, with complementary stems 30 a,b respectively. 

1. A combination vent and cover for a tank, comprising: a circumferential base plate adapted to fit over a port of a tank and seal the tank, the base plate having a bolt hole pattern coinciding with a bolt hole pattern of the tank; an integral stem formed centrally in the base plate projecting outwardly from the plate; a vent sized to fit over the stem and connect to the stem, the vent allowing the tank to dispel air as the tank is being filled.
 2. The combination vent and cover for a tank of claim 1, further comprising a mushroom cap for the vent.
 3. The combination vent and cover for a tank of claim 1, further including a removable flange about the base of the vent for allowing the vent to attach to other tank configurations.
 4. A double molded manway cover for a tank having a first cover molded to a second cover, each cover having a circumferential base plate adapted to fit over a port of a tank, and an integral stem formed centrally in the base plate of each manway cover, where both covers are formed in a single molding operation and separated to yield two covers.
 5. The double molded manway cover for a tank of claim 4 where one manway cover has a larger diameter than a second manway cover.
 6. The double molded manway cover for a tank of claim 4 where both manway covers have the same diameter.
 7. A tank for storing materials comprising: a storage compartment defined by a plurality of surfaces and a conical upper wall with a manway opening; a manway cover adapted to cover the manway opening, the manway cover including a vent structure for venting the tank when material is forced into the tank.
 8. The tank of claim 7 wherein the vent structure is a mushroom vent built into the manway cover. 